Department of Medicine, Program in Molecular Medicine, Department of Internal Medicine, Division of Cardiovascular Medicine, Department of Pathology, University of Utah, Salt Lake City, Utah, United States

Purpose :
DR is one of the fastest growing causes of blindness and visual impairment in the working age population. State-of-the-art pharmacological therapies often rely on anti-VEGF to dampen pathologic vascular leakage and neovascularization(NV). However, the identification of new targets and the development of new therapeutic strategies for DR are vital. Here, we show that a small GTPase ARF6 is a convergence point for many angiogenic and inflammatory pathways and is a key player in the pathologic progression of DR. We thus hypothesize that the inhibition of ARF6 will reduce vascular permeability and NV as well as their debilitating sequelae.

Methods :
VEGF, IL-1β and TNFa signaling pathways were activated in cultured human retinal endothelial cells (HRECs) to determine the common role of ARF6 in regulating those diabetic pathophysiological pathways following either ARF6 knockdown or small molecule inhibition and assessing structural/functional changes. The molecular mechanism in which ARF6 controls endocytic trafficking of cell junction proteins and receptors involved in permeability were determined. Reveal levels of ARF6 in diabetic human and mouse eyes were measured. Mice deficient for Arf6 or wild type mice treated with ARF6 inhibitor NAV-2729 were used in mouse models of DR, including oxygen-induced retinalpathy (OIR) to test NV and streptozotocin (STZ)-induced diabetes to test retinal vascular permeability.

Results :
ARF6 plays a critical role in controlling cell signaling and function by regulating endocytic trafficking of cell surface proteins including VEGFR2 of which internalization is critical for downstream signaling and cell junction protein VE-cadherin, which is important for maintaining cell barrier function. ARF6 expression and activation levels are increased in eyes from diabetic human and mouse. The mice lacking endothelial specific Arf6 expression have reduced VEGF- and IL-1β-induced retinal permeability. NAV2729 reduces VEGF- and STZ- induced retinal permeability in mice to levels comparable to those treated with the anti-VEGF drug, as well as inhibiting retinal NV in OIR model.

Conclusions :
Using a combination of in vitro, cellular, genetic, and pharmacologic techniques, we demonstrated that ARF6 is pivotal in trafficking of junction proteins and receptors, and that targeting ARF6-mediated trafficking has potential as a therapeutic approach for retinal vascular diseases such as DR.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.